I chose debian for the base of Kwheezy for many reasons, but ultimately, debian is perfect for building on top of. It's well known that debian is rock solid stable, perhaps even the best tested distro in the GNU/Linux world. It also has a fantastic security team and a repository dedicated to security updates (patches). Debian also has a well designed package management system, so installing, updating and repairing a debian system is a breeze. So it's stable, secure, easy to maintain, all of which makes it perfect for servers. However, this comes at a cost, and that cost is that the software in it's huge repositories is old. It has to be old to be so well tested, patched, tested, patched... and so on . Not just as individual applications, but how well they integrate with the rest of the system. And of course; debian is only ready when it's ready. There aren't many software projects with that attitude these days.
So it's obviously a good choice for servers, but what about desktop computing. Debian is not the most user-friendly distro. It does not have a super easy installation utility. It is not made all nice and pretty, it mostly sticks to upstream defaults. It does not do any user specific configuration, not at a desktop computing level anyway. You, as the user are expected to learn and configure your system to suit your needs. You are expected to bend the law to make that audio/video track play. This is the way that many advanced Linux users prefer it to be. But it's not the way that beginers, newcomers, lazy's or too busy to's like it to be. And the extra work is, unfortunately, enough to put many people off from settling with debian.
It's for these same reasons that debian is such a good base for a distro. Stable and well intergrated, with a huge repository of well tested applications, but without creating constraints. Without adding unnecessary complexity. There is a trade-off for user friendly simplicity. And prettiness is subjective, each to their own. Debian gets all the technical underpinnings done well, and allows a distro maker to apply their polish.
So that's the technical background. But why did I personally choose debian?
I started my own journey in the Linux world with a distribution I shall not name, it was distinctively brown, or at least it was in those days. I used it for a couple of years at least. I had great fun, and gained some good linux experience with it. I never really had many problems that didn't apply to Linux in general. It was debian based, so I came to know and love the deb package format, or more so, apt-get. But by this time I started trying out other distro's, and naturally, other desktop environments. Even though I had been on Gnome 2.x for a long time, and gotten used to it, and it did everthing I needed it to do. I decided that I liked KDE better. I liked the looks, the customizability , the power; despite the early stages of KDE4 being buggy and slow. It was also perhaps that I'm a software developer. I wanted to pick a single GUI toolkit to learn and start developing Linux applications with. I was drawn towards Qt, and hence KDE was more suitable. These two factors compounded each other. But alas, my distro was firmly based on Gnome, what to do.
Now to find a new distro. One that supported KDE, one that loved KDE. My previous distro had a brother with KDE, but it was, at least at that time, not a great implementation of KDE. But I also wanted to stick with deb and apt-get. So, let's find a KDE-centric distro that uses deb and apt. There really wasn't a lot to choose from. Most of the KDE-centric distros were rpm based (Mandriva, OpenSUSE) or too difficult (Slackware, Arch, Sabayon) or they were just not mainstream enough. Debian itself was less appealing for the reasons expressed above. Also, debian's KDE was too old at that time, KDE3 was superseded and KDE4 had to be recent to be stable.
To add to the complexity of my decision; I started to build a Linux based roll-out for my company, where I am IT manager. So I needed something I could build on top of, without any experience in distro building and being an intermediate Linux user at best. Somehow I ended up using PCLinuxOS, of which our roll-out is still using today, until the debian based one is ready. Despite it being rpm based, at least it used apt-get and synaptic. It is very highly customized and without doing so in packages, so I can't even remember where all my changes are. It was very nearly based on Mepis, which had a significantly newer KDE than debian, and kernel. In fact perhaps the only reason it wasn't based on Mepis was that Mepis didn't have a remastering tool. PCLinuxOS has it's own remastering tool called "MyLiveCD" (formerly "MakeLiveCD"), which was perfect for making our roll-out with. It is also a great KDE distro, with excellent hardware support. And amazingly, for a rolling release, it is incredibly stable. The biggest downside with PCLinuxOS, at that time, was that being a one man show, it had a noticably smaller repository. Whilst having most common home computing software, it lacked some I needed in a corporate environment. RPMs from other distros didn't work, but i discovered deb's from the debian repository worked best, converted using 'alien'.
It was from my experience building a roll-out for my company that I came to appreciate debian as a base for a distro. Whilst PCLinuxOS was very stable, it was still a rolling release. A moving target really becomes a problem for a corporate roll-out. It took me over a year to get all the kinks ironed out of our roll-out, to get it to suit everyones needs. Whilst a linux enthusiast will put up with endless breakages and workarounds, they can just visit their forum and find a solution. Common office workers, which don't want to be pried from the clutches of their beloved Windows XP, are much less tolerant. We ended up mirroring the PCLinuxOS repository and freezing it, simply by not updating our mirror. Effectively doing what debian does, but without the 6-12 months of testing and patching. And now we're mostly on noticably older versions than in the current debian stable repository.
Debian stable is perfect for a roll-out or a distro because it is so predicatable and dependable. It simply works! There is rarely an annoying and silly bug getting in your way of doing real work. Because the debian developers and packagers have already ironed out every single release-critical bug. As a distro developer, I take great comfort in the fact that my customizations will not be broken by an update. The updates are far fewer than most other stable distros. Debian stable updates very rarely break anything. They are mostly for security patches, which is something you definetely want.
So what if the software is a little old. KDE 4.8.4 has fully evolved, it's more than I could ask for. Debian stable works like a dream, it gets the job done, then gets out of my way. It allows me to get my work done without any hair-pulling and wasted time wading through forums and bug reports for fixes. It's also one of the fastest distros out there.
A big thanks to all the wonderful people involved in the Debian project. Debian wheezy is a fantastic release. Thanks for giving me a perfect base for my distribution.